A new U.S. military intelligence assessment says for the first time that North Korea may have developed a nuclear device small enough to mount on a ballistic missile, but said such a weapon's "reliability would be low."

In an assessment by the Defense Intelligence Agency, a branch of the Pentagon, analysts appeared to upgrade U.S. estimates of North Korea's nuclear-weapons abilities, according to a portion of the report disclosed by a lawmaker at a House hearing on Thursday.

Secretary of State John Kerry will press China to more aggressively muscle North Korea on his inaugural trip to the region as America's top diplomat. Robert Ourlian reports.

There was disagreement in Washington over the extent of North Korea's capabilities, with Obama administration officials and the Pentagon press office saying there isn't evidence that the country could use such a weapon.

Tensions are running high in Washington over how best to address the North Korean threat without triggering precipitous reactions from U.S. allies in North Asia. The White House has made an effort to rein in tensions and more tightly control the message, but as the varying interpretations of Pyongyang's abilities show, that can be difficult on politically charged issues.

The Defense Intelligence Agency, or DIA, rated its confidence in its finding as "moderate." Experts said that, if proven accurate, the assessment would mark a dangerous advance in the North Korean program.

"It's more forward-leaning about the threat than they've previously said," said a staff member of the House Armed Services Committee who has read the DIA report. "Clearly, they are very alarmed, and the information they are seeing shows a great deal of alarm—and now more information is coming out for the American people to see."

ENLARGE

North Korean military officers in April on a sight-seeing boat on a China-North Korea border river.
Associated Press

Rising Tensions on the Korean Peninsula

Threats by North Korea against its southern neighbor have escalated, deteriorating fragile relations between Pyongyang and Seoul. The threats are an annual occurrence during U.S. military exercises in South Korea but have been particularly vociferous this year.

Leaving North Korea

South Korean vehicles carrying products used and produced by South Korean companies in North Korea's Kaesong Industrial Complex arrived at a border crossing in Paju, north of Seoul, on Wednesday. Reuters

The disclosure came as John Kerry arrives Friday in Asia for his first tour as secretary of state through a region more on edge than it has been in years. North Korea has threatened to launch missiles and South Korea has vowed to retaliate against hostile acts.

Mr. Kerry will visit South Korea on Friday, China on Saturday and Japan on Sunday. He plans to press Beijing to more aggressively muscle North Korea away from its military and nuclear threats, senior U.S. officials said.

Mr. Kerry also will reassure South Korea and Japan that the Obama administration is committed to their defense and to shifting the U.S. national-security focus toward Asia and away from the Middle East.

Paving the way for Mr. Kerry's visit, President Barack Obama exhorted the North Koreans to tone down their rhetoric and said he favored diplomatic engagement, but said the U.S. would take "all necessary steps" to protect its interests.

His comments came after an Oval Office meeting with United Nations Secretary-General Ban Ki-moon, who urged China to exercise its influence over North Korea "so that this situation will be resolved peacefully."

The DIA assessment was first divulged Thursday at a hearing of the House Armed Services Committee, by Rep. Doug Lamborn (R., Colo.).

"DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles," according to the unclassified conclusion of the March threat assessment provided to lawmakers. "However, the reliability will be low."

Following the disclosure at the House hearing, the Pentagon issued a statement saying it "would be inaccurate to suggest that the North Korean regime has fully tested, developed, or demonstrated the kinds of nuclear capabilities referenced in the passage. The United States continues to closely monitor the North Korean nuclear program and calls upon North Korea to honor its international obligations."

Late Thursday, James Clapper, the director of national intelligence, issued a statement backing up the Pentagon's statement. He added that the DIA finding wasn't an assessment from all 16 intelligence agencies, saying "North Korea has not yet demonstrated the full range of capabilities necessary for a nuclear armed missile."

South Korea's military doesn't believe North Korea has a nuclear weapon small enough to mount on a missile, a defense ministry spokesman said Friday.

Earlier, at a separate hearing in Congress, Mr. Clapper played down the latest spate of escalatory talk, suggesting it was bluster. "All of the belligerent rhetoric of late, I think, is designed for both an internal and an external audience," he said. "But I think first and foremost it's to show that [ Kim Jong Eun] is firmly in control in North Korea."

Mr. Clapper did reiterate the collective assessment of U.S. spy agencies that "North Korea has already demonstrated capabilities that threaten the U.S. and the security environment in East Asia."

Senior Obama administration officials said Thursday that the White House hasn't seen evidence that the North can successfully put a nuclear weapon on a missile, despite progress over the years.

"North Korea has launched missiles and successfully put a satellite in orbit in December, so we know that they have long-range missile technology. We know that they have a nuclear capability and have stated their intention to use it together with their missile capabilities. They've made progress over the past several years in developing both of those elements and that is concerning to us," a senior administration official said.

"But we've not seen any evidence that they've actually been able to marry up their nuclear technology with their missile capabilities. They've certainly not successfully carried out these intentions," the official said.

The administration, the official said, will "continue to monitor the situation and take prudent steps to protect ourselves and our allies."

By releasing the intelligence assessment, House Republicans injected more concern about the North Korean threat into the public debate. Committee staff members said Rep. Lamborn had checked the assessment with the DIA before making the information public to ensure that the conclusion was accurate and unclassified.

The DIA is one of more than a dozen U.S. spy agencies, and it wasn't known whether its conclusion was shared by other intelligence analysts.

Analysts said the intelligence assessment is an indication of growing concern within the administration over the increasing nuclear threat from North Korea.

"North Korea's ballistic-missile and nuclear threat is very much a near-term threat," said Victor Cha, a specialist on North Korea at the Center for Strategic and International Studies. "For people to say it's just bluster, well, the bluster may be harmless, but the steady progression in their program is not harmless."

North Korea has said its nuclear test in February involved a miniature device, a description U.S. and international experts said at the time could mean the government had developed a warhead small enough to mount onto a missile.

In recent weeks, the U.S. has demonstrated its increasing concern about the threat from North Korea by bolstering its missile defenses in the region.

The Pentagon has said it would spend about $1 billion to add 14 extra missile interceptors in Fort Greely, Alaska. The ground based interceptors are meant to destroy long range missiles launched by North Korea to the U.S. There are currently 30 interceptors in Alaska and California.

While the additional interceptors won't be ready until 2017, the Pentagon has taken more immediate steps to bolster missile defenses in the region. It has sent ballistic-missile-defense ships off the coast of South Korea. It also said it would deploy the Army's Terminal High Altitude Area Defense system to Guam, to protect the military base there from midrange North Korean rockets.

Mr. Kerry is expected to face major challenges in selling U.S. assurances to a North Asia that is at its most combustible state in decades. North Korea's recent nuclear-weapons tests, missile launches and threats are fueling nationalistic calls in Seoul and Tokyo for those countries to respond and significantly enhance their own defenses.

The drive is being fed by concerns over the U.S.'s financial position and Washington's ability to defend its Asian allies long-term, these diplomats and analysts said.

"Of all the issues I heard while in Asia, getting our fiscal house in order was No. 1," said Sen. Bob Corker (R., Tenn.), who met with South Korean President Park Geun-hye recently in Seoul, and discussed the North Korea crisis.

The new Chinese government of President Xi Jinping is also expected to test Mr. Kerry and the Obama administration's commitment to "pivot" its strategic focus to Asia, when he visits Beijing starting on Saturday.

Mr. Kerry's predecessor, Hillary Clinton, was viewed in Beijing as the driving force behind the U.S.'s more aggressive posture in Asia in recent years, said Chinese government officials and analysts.

Her high-profile challenging of Chinese territorial claims in the South China Sea, beginning in 2010, infuriated Beijing's leadership.

Mrs. Clinton also was the lead U.S. voice criticizing China's positions on Internet freedom and cyberwarfare. And she worked to strengthen Washington's relations with China's closest neighbors, helping to orchestrate a U.S. rapprochement with Myanmar's military government in 2012.

Several Chinese experts on foreign policy have suggested in recent weeks that they believed Mr. Kerry will be less "aggressive" than Mrs. Clinton, and would place greater emphasis on the economic and other nonmilitary aspects of this refocusing on Asia.

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